In a manufacturing of a semiconductor device, various processes such as film formation, etching and the like are repeatedly performed on a semiconductor wafer to manufacture a desired semiconductor device. Recently, in order to meet demands for high-speed semiconductor device, miniaturization of a wiring pattern and high level of integration, it is required to realize low resistance of wiring (high conductivity) and high electromigration resistance.
In view of the above, Copper (Cu), which has a higher electromigration resistance and a higher conductivity (lower resistance) than those of aluminum (Al) and tungsten (W), is being used as the wiring material.
The Cu wiring is formed by filling Cu in a trench or via formed in an interlayer insulating film, but in order to prevent Cu from being diffused in the interlayer insulating film, a barrier film is formed before filling Cu.
As a method of forming the barrier film, there is used a method of forming a tantalum (Ta) film, a titanium (Ti) film, a tantalum nitride (TaN) film, a titanium nitride (TiN) film or the like physical vapor deposition (PVD). However, with a further miniaturization of a wiring pattern, it is difficult to obtain a sufficient step coverage by the above-mentioned method. Accordingly, there is examined a method of forming as the barrier film a mangane oxide (MnOx), film by chemical vapor deposition (CVD) or atomic layer deposition (ALD) which can form a thin film with a good step coverage. The MnOx film, however, has a low adhesion to Cu film, and there has been proposed a Cu wiring forming method in which a Ruthenium (Ru) film having a high adhesion to Cu film is formed on the MnOx film and a Cu film is formed on the Ru film (see, e.g., Japanese Patent Application Publication Nos. 2008-300568 and 2010-21447).
Meanwhile, when forming the Ru film on the MnOx film, it is difficult to make the Ru film have a good surface state since a nucleus formation density of Ru is low. Accordingly, there has been proposed a technique in which a hydrogen radical process is performed after the MnOx film is formed and then the Ru film is formed thereon (see, e.g., PCT Publication No. 2012/173067).
However, with a further miniaturization of a semiconductor device, the aspect ratio of a recess such as a trench or the like is increased. Accordingly, even with the technique disclosed in PCT Publication No. 2012/173067, it is sometimes difficult to form a continuous Ru film with high step coverage on the MnOx film in the recess or to form a Ru film having a good surface state, which may result in a poor filling of Cu.